Visualization Sealing Simulation Test and Evaluation of Hard Brittle Shale Microfracture

In order to understand the sealing mechanism of microfracture in hard and brittle shale,a series of tests have been conducted using the newly developed visual microfracture sealing evaluation instrument.Many kinds of LCMs had been evaluated in the test,including single and combined LCM.Filter loss and sealing pressure were used as the criterion of sealing capacity.Based on the sealing capacity criterion and visible fracture sealing condition,seven simulated fractures with different apertures were evaluated in this article.The results showed that filter loss and sealing pressure difference did not have a linear relationship. Maximum LCM performance could be achieved when fracture aperture was equal to D50-D58 of the LCMs.Better performance would not be achieved with the increment of rigid LCM concentration.The optimum mass fraction range of deformable sealing particles was 0.5%-0.7%.Three different seal locations had been observed in the fracture,and the best sealing performance was achieved when the seal formed in the middle of the fracture.The research results showed that the hard and brittle shale microfracture sealing simulation method was feasible,and it was useful to the further study of the sealing mechanism of microfracture.